B+K precision 5490C Series, User Manual

Page: 44 / 57

36
(4) Configure the serial communication
Press Menu
→
Utility
→
I/O config to enter the port configuration interface. Select the RS232 option
to configure RS232 communication.
Select the Baudrate option to set the baud rate.
Select Data bits to select the data bits.
Parity: Select the check mode. There is no check bit by default.
Stop bits: set the stop bit, default 1 bit.
(5)
Software Protocol
Since the hardware communication check (handshaking lines CTS and RTS) is not used in the RS232
interface, the multimeter uses the character return method to reduce the possibility of data loss or
data error in the communication. Please refer to the following when compiling computer
communication software:
1.
For command syntax and format, refer to Chapter 8 Command Reference.
2. The controller transmits the command using the ASCII code with <LF> as the terminal character.
The multimeter executes the command after the terminal character is received.
3. The character received by the multimeter will be sent back to the controller again. The controller
will not send the next character until the last returned character is received correctly from the
multimeter. If the controller fails to receive the character sent back from the multimeter, the
possible reasons are listed as follows:

The serial interface is not connected correctly.

Check if the multimeter has opened the RS232 interface function and the baud rate is
selected correctly.

When the multimeter is busy with executing a bus command, it will not accept any character
from the serial interface at the same time. So the character sent by the controller will be
ignored. In order to make sure the whole command is sent and received correctly, the
character without a return character should be sent again by the controller.
4. The multimeter only sends information under the following two conditions.

When a character is received normally, the multimeter will send the character back as a
handshake.

When a query command is received, the multimeter will send the query response
information.
5. Once a query command is received, the multimeter will send the query response information
immediately even if the rest commands have not been finished. So if the command includes two
queries, the controller should read the query responses twice. One query is recommended to be
included in a single command.
6. A query response is sent out in ASCII codes with the preset terminal character.
7. Several query responses will be sent continuously with a 1ms interval. The controller should be
ready to receive the responses; otherwise the response information will be lost.
8. The controller should receive the query response terminal character. Otherwise you will confuse a
terminal character with a returned character. At the same time the controller should receive the